Mouse skipping problem when external display connnected

One more thing. I went out and bought an Apple 23" Cinema Display with Mini DisplayPort connector, thinking that perhaps there was something funky with the Mini DisplayPort to DVI adapter. I still see the cursor tracking issues on this monitor, so it's not the use of a DVI adapter doing it. It was an expensive test, but this problem was driving me nuts. Now I have a crappy display that has a whole bunch of other issues (off topic).

I am having the exact same issue. The mouse and keyboard stop or freeze at an interval of about every three seconds.

It's very predictable and exact

I've been experimenting... I typically have many (30+) folders on my desktop. I recently got rid of all but one and it seems to make the mouse lag happen less. Now please understand, this is very unscientific, it could be just me, or it that could be the issue.

Would someone else be willing to try removing all the folders/icons from your desktop (Except mounted drives) and see if that makes things go faster for you. I'm curious.

mine did it with a brand new imac, so pretty much nothing was on my desktop. One of the first things I did was attach the other monitor after the initial setup, and it was immediate. I tried using a USB mouse, then an older mighty mouse, then a USB Keyboard... it has to be hardware specific because it doesn't happen on my macbook, that doesn't have the Mini DisplayPort.

OK. Thanks for that feedback. So then tt seems that it's entirely Mini DisplayPort related. I also had an older MacBook Pro with DVI connector... it never had this issue, and I used it with an external monitor attached 90% of the time. Hopefully this is a software related issue that Apple can fix with a future update to OS X and not hardware related. If it's the later, seems that we're all SOL.

I often wonder why Apple does things like switching from DVI to Mini DisplayPort. I know they like to be on the bleeding edge of technology, but sometimes I wish they'd think about the implications before they make major changes to the hardware. Nobody makes a Mini DisplayPort monitor. And no hardware manufacturers have any plans to. Hey Apple, how about using Mini DVI? It's more common, and it has the word "Mini" in it, just like Mini DisplayPort.

Just my $0.02

yeah, it's very strange that this didn't show up during some type of testing phase of the product, considering it's not mac model specific, anything with a Mini DisplayPort seems to have the issue. to be quite honest, i'm a little disappointed at this point, its not like this is a brand new piece if hardware.

I have the same issue on my 27" iMac. Every 3 seconds or so, the mouse freezes for about half a second.

I had a Dell 24" 16:9 LCD connected and it was driving me insane. I have had to disconnect this display so I can work on the machine again. As big as the 27" screen is, im used to working with quite a bit more screen real estate.

One thing I have noticed, it only seems to be input devices that lock up, if I am playing a DVD or a video, it does not freeze.

It appears to be 8 months since this problem was originally reported. I found this thread after putting my new Mac Pro into service. Took we awhile, swapping in several different kinds of mouse - wired and wireless, before realizing that turning off my second display will immediately stop the erratic behavior of the cursor ( as described many times in this thread ). In my case, the cursor seems to freeze, then "catch up" with my mouse movement after a half-second.

My primary monitor is on dual-link DVI ( 30" cinema display ) and the secondary monitor is on the mini-displayport (24" EIZO). I arrange the monitors in the extended desktop configuration.

I'll make my own call to Apple support now. Thanks for everyone's comments - now I know it's not just me...

Solution (for macbook) finally found! I was using my macbook in clamshell mode with BT mouse/keyboard combo + samsung lcdtv via Hdmi and experiencing massive mouse lag with my bluetooth mouse. The only thing that works is to leave the lid to the macbook OPEN and withount any obstuctions in front of the mouse. I set my mac to never sleep and have not had any lag for weeks...ah, so nice. I hope it works for all.

I have the same problem with my new iMac and a 2006 ViewSonic monitor using DVI. This must really be related to the mini display port. Quite a letdown. Seems like getting a VGA adapter is the only "solution" right now (and it's obviously not acceptable).

Edit: Also tried USB mouse - same problem, so not a bluetooth issue (like most respondents here)

Message was edited by: Kai Brinker

For me it's not just the mouse - it's the keyboard too (bluetooth in my case). Tried holding down a key and got about four seconds of repetition, followed by a split-second lag, then it continues.

I actually also have this problem on my white Macbook 13", bought in 2009. The problem is when using a DVI adapter, VGA adpater works fine. This model does not accept an s-video/component adapter (even though they fit in the slot).

As for my MB PRO 15", it is the same as everyone has reported. None of the machines have the problem when booting directly into Windows XP.

Sitting here with a 27" iMac-i7 (only 14 days new) with a generic 19" second monitor. Mouse AND keyboard would stop responding every 3.5 seconds (i.e., opened TextEdit and "sat" on the "a" key while spinning the mouse in a circle on the screen... both would stop simultaneously every 3.5 seconds and then both restart [simultaneously] a second later). Determined the hesitation was due to the MiniDisplayPort-to-DVI adapter.

Testing:
- Switched to a MS keyboard (wired and wireless)... same results
- Switched to a MS wireless mouse and a generic USB mouse... same results
- Switched one DVI adapter for another DVI adapter, same results.
- Switched from a DVI to VGA adapter... problems disappeared.
- Disconnected the second monitor... problems disappeared.

Guessing:
Since the MiniDisplayPort and DVI provide 2-way communications, perhaps the iMac is looking for "a reply" from the second monitor every 3.5 seconds (and locking-out the keyboard and mouse momentarily).

While sad that I need to switch to analog (VGA) from DVI, the second monitor is really just a "sidecar" for email and PSD/ILL/IDD menus. Seems there are other posts that are similar (thanks to those posts, we figured out the problem). I leave it to the Apple Engineers to replicate and resolve. Cheers!

Just a note that the 27" iMac firmware update that came out last week did not resolve this problem.

I'm also looking for a solution to this. Seems to have started after the last ProKit software update (which also messed up Compressor). I've wiped everything and reinstalled, but still have the mouse lag/freeze problem.

Any suggestions as to why this is happening would be greatly appreciated.